Intro to Bacteria Flashcards
Structure of a bacterium
- Capsule
- Cell wall
- Plasma membrane
- Cytoplasms, ribosomes
- Single chromosome, no nucleus
- Flagellum
- Fimbriae - attachment
Describe Gram positive cell wall
- Plasma membrane
- Periplasmic space
- Peptidoglycan
Describe Gram negative cell wall
- Plasma membrane
- Periplasmic space
- Petidoglycan
- Another Peri. space
- Lipopolysaccharide nd protein outer membrane
Difference between cell wall of gram pos. and neg.
Negative has enter Periplasmic space and outer membrane of lipopolysaccharide
-Pos. has thick peptidoglycan wall with techoic acid and neg. has thin
What is the gram stain appearance of Gram positive?
Purple due to thick peptidoglycan wall
What is the gram stain appearance of Gram negative?
Pink
What is the shape of cocci?
Spepherical
What is the shape of bacilli?
Rod shaped
What do penicillin binding proteins do and name examples
Cross link peptidoglycan chains to form rigid cell walls
- Transpeptidases
- Carboxypeptidases
- Endopeptidases
What is peptidoglycan?
Strong carbohydrate polymers cross linked with 3/5 amino acids
Function of the capsule
Helps bacteria to survive in host system and prevents it being phagocytosed
Describe the different types of Flagellum
- Montrichous - 1
- Lophotrichous - all at one point
- Amphitichous - both sides
- Peritrichous - all over
Give examples of bacteria with flagellum
Eacherichia coli and salmonella enterica
Function of fimbriae
Allow adhesion and cause infection
Use of spores by bacterium
Ensures survival of bacterium during environmental stress
-Resistant to UV, gamma rays, desiccation, temp, starvation and chemical disinfectants
Function of Periplasmic space
Contains enzymes important for digestion of materials, transporting material and detecting chemical gradients in environment
What are plasmids?
- Small, circular, double stranded DNA
- Can replicate independently
Bacterial conjugation steps
- Donor cell (F+) produces pilus
- Pilus attaches to recipient cell (F-)
- Single strand of DNA from plasmid transferred to F-
- Both cells synthesise complementary strand
How to bacterium replicate?
Binary fission (asexually)
How is variation introduced?
Spontaneous mutation (random) and transfer of DNA - dead cells present containing DNA and if it’s advantageous then it is taken up
Describe process of binary fission
- Cell replicates DNA
- Cell elongates, separating DNA molecules
- Division of bacterium - cytokinesis
- Two new daughter cells (genetically identical)
What is a bacteriophage?
A virus which attacks bacteria and lyses them
Describe detection and culture of bacteria
- Individual bacteria can only be seen with microscope and gram staining
- Colonies of individual bacteria cultured on solid medium (agar and then can be seen by eye
Bacterial nomenclature
- First part (i.e. staphylococcus) is genus
- Second part (i.e. aureus) is the species
What technique is used to identify strained of a species?
DNA typing
-Strains of species have similar characteristics
